variable DC supply

variable DC supply

Hi, i am new to multisim and in need of guidance. i cannot find a variable DC voltage supply that i can change on the fly while simulating. The labs i am assigned require me to change the DC voltage until a specific reaction is obtained. Can someone tell me if there is a component in multisim that is able to do this?

PS. i am unable to squeeze in as much lab time at school because of my jobs.